In fuel-fired, in particular gas-fired, industrial furnaces it is possible to partially recover the flue gas heat by preheating the air.
Regarding this, document DE 195 419 22 A1 describes a burner with a ceramic recuperator that has the form of a tube-shaped ceramic element. The latter is provided on the pipe outside as well as on the pipe inside with pin-like projections that are disposed to enlarge the surface of the recuperator pipe. Flue gas flows around the outside of the recuperator pipe. Air to be heated flows in opposite direction on the inside of the recuperator pipe into the furnace chamber. With such a ceramic recuperator acting as a counter-flow heat exchanger it is possible to recover flue gas heat from very hot flue gases having a temperature of 1250° C., for example. Experience has shown that a combustion-specific efficiency of 65% to 70% is achieved.
From document DE 1232304 A a recuperator burner for heating a radiant pipe has been known, in which case this recuperator burner comprises a heat exchanger that is perfused by fresh air for cooling the wall-side flange and the wall, said heat exchanger concentrically enclosing the recuperator pipe.
Furthermore, from document EP 1 995 516 B1 a recuperator burner has been known, wherein said burner comprises a manifold of flattened fresh-air conducting pipes disposed for preheating the air, said manifold of pipes being arranged in an annular chamber in an flue gas flow leaving the furnace chamber. With the use of this recuperator it is possible to improve the preheating of the air and increase the efficiency to over 80%. However, the use is limited to flue gas temperatures up to approximately 1000° C. Therefore, in particular considering low-efficiency industrial burners of under 200 kW, the object to be achieved is a high combustion-specific efficiency at justifiable expense and at high flue gas temperatures.